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Hyperloop lets you travel on a resonant acoustic wave?

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Re: Hyperloop lets you travel on a resonant acoustic wave?

#71

Post by rorrr2 »

VLM wrote: post #59
rorrr2 wrote: post #49

Earlier quoted context omitted.

Either way, pretty much any accident will result in everyone's death. Car accidents at 50 MPH result in 80% death. 760 MPH is much much much more, considering the amount of energy needed to be dispersed grows quadratically (E = 0.5 * m * v^2)

"Car accidents at 50 MPH result in 80% death." Actual stats from Great Britain in 2008 on motorways, presumably always speed limit above 50 MPH, "6% of the total killed, 3% of total seriously injured, 5% of total with slight injuries." at least per wikipedia. So there's about a 9 in 10 chance if you crash on a GB motorway, at least in 2008, you'll walk away without a scratch, rather than your 1 in 5 stat. Also all mi…

You are confusing the speed limit with the speed at which the crash happens. Most people apply breaks before the crash, and do not crash at full speed.

http://www.swov.nl/rapport/Factsheets/UK/FS_Speed.pdf

Though that number is always going down, because modern cars are safer than previous gens.

Re: Hyperloop lets you travel on a resonant acoustic wave?

#72

Post by pedalpete »

niels_olson wrote: post #42

As a surfer, let me volunteer that it's a bit like a highway onramp: you want to match speed exactly when the front arrives. Tiny adjustments in speed, pitch, yaw, roll, and center of gravity make the difference between making it, falling off the back, and getting eaten. Mistiming your drop leads to bad outcomes that are directly proportional to the kinetic energy of the wave and are inversely proportional to the dep…

I'm somewhat new to surfing but am thinking this is slightly different than what you are imagining. I also know next to nothing about acoustics and wave forms.

Wouldn't the wave be the height of the tube, and the vehicle be near that same height? That way you can't "miss" the wave. Unlike surfing their is no room below the wave for the vehicle do dive and throw the surfer off, and unlike surfing , a soundwave (to my knowledge) doesn't break, so there is no tumble. If you enter at the point where you're off the back of the wave, you're positioned to be picked up by the next wave, which because your vehicle height is near equal to the height of the wave, your vehicle automatically gets pushed along.

That's how I'm visualizing it, but I could be wrong.

Re: Hyperloop lets you travel on a resonant acoustic wave?

#74

Post by gliese1337 »

PaulHoule wrote: post #50
foobarqux wrote: post #45

Earlier quoted context omitted.

I wouldn't mind the article if it contained some kind of real analysis as to feasibility from a physics and engineering perspective. That type of analysis would be interesting independent of hyperloop.

Worst of all this article is just a rip-off (a paraphrasing) of another article. He is kind enough to point to the original article, but he isn't adding anything new, just putting the old wine in new bottles.

No, it's not. The pointed-to article says that if you travel with the density peak of a sound wave, you get reduced drag, but you'll need some other system (like a railgun / gauss gun) to actually provide propulsion. This article says "I bet it's more than that, I bet the sound waves are actually providing the driving force like in this cool YouTube video of acoustic levitation."

Re: Hyperloop lets you travel on a resonant acoustic wave?

#75

Post by andrewcooke »

jessriedel wrote: post #19

I can't figure out how the OP proposal differs from Charles Alexander's. Low frequency (long wavelength) waves travel around the tube at the speed of sound. By traveling at the same speed, and correctly choosing a point along the wavefront, one can take advantage of significantly reduced apparent drag. It's implicit in Alexander's suggestion that either (a) the total length of the loop is an integer multiple of the w…

it's slightly less wrong, as far as i can see - http://www.acooke.org/cute/HyperloopW0.html

Re: Hyperloop lets you travel on a resonant acoustic wave?

#76

Post by kolev »

bencoder wrote: post #54

The hyperloop is feeling like the segway at the moment. I remember the hype before the reality of the segway and everyone being disappointed when they found out it was just a slightly altered scooter.

Segway was a business with patents, investors, and stuff. This is a gift to the humanity although if somebody has to implement it, it will be Elon Musk, I'm sure.

Re: Hyperloop lets you travel on a resonant acoustic wave?

#78

Post by johnpmayer »

pedalpete wrote: post #72
niels_olson wrote: post #42

As a surfer, let me volunteer that it's a bit like a highway onramp: you want to match speed exactly when the front arrives. Tiny adjustments in speed, pitch, yaw, roll, and center of gravity make the difference between making it, falling off the back, and getting eaten. Mistiming your drop leads to bad outcomes that are directly proportional to the kinetic energy of the wave and are inversely proportional to the dep…

I'm somewhat new to surfing but am thinking this is slightly different than what you are imagining. I also know next to nothing about acoustics and wave forms. Wouldn't the wave be the height of the tube, and the vehicle be near that same height? That way you can't "miss" the wave. Unlike surfing their is no room below the wave for the vehicle do dive and throw the surfer off, and unlike surfing , a soundwave (to my…

(experienced body boarder/body surfer, novice actual surfer ;-)

I think the point is that, regardless of which wave you decide to catch, whether it be the first or second one, at some point to need to sync-up. If you miss the first one, then you still have to speed up or you're going to miss the second one too.

There's definitely an optimal timing that takes the minimum amount of energy to accelerate and synchronize with the "sweet spot" of the wave; beginners need to paddle early and paddle hard, whereas an expert has a better feel for it and will exploit his or her experience with the timing to expend less effort catching a wave.

When you surf, paddling up to speed and the timing will make or break catching a particular wave - which is very important is the "good waves" are rarer. With an acoustic loop, it's may be more predictable, but you still probably want to get it right the first time, while you're still in the main accelerator section of the tube.

Re: Hyperloop lets you travel on a resonant acoustic wave?

#79

Post by enko »

pjscott wrote: post #38
enko wrote: post #14

Earlier quoted context omitted.

It does on HN : P Well, the acoustic idea wouldn't solve drag at all. The craft would still have to move through air.

I refer you to Charles Alexander's idea, which goes through a bit of the math for why traveling with the peak of an intense, low-frequency sound wave would give freakishly low drag. http://charlesalexander2013.wordpress.com/2013/07/18/hyperlo...

Ah, I see. That's an interesting idea. Sounds impractical - if you're going to do all that engineering work, might as well just get rid of the air in the first place - but cool concept.

Re: Hyperloop lets you travel on a resonant acoustic wave?

#80

Post by ricardobeat »

bencoder wrote: post #54

The hyperloop is feeling like the segway at the moment. I remember the hype before the reality of the segway and everyone being disappointed when they found out it was just a slightly altered scooter.

The hype before the Segway was so immense, that even if they announced something exactly like the Hyperloop people would have felt disappointed. People actually considered anti-gravity belts to be a possibility at the time.
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